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Subject: Re: Evaluation in Rebel

Author: Ed Schröder

Date: 04:17:27 01/07/03

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On January 07, 2003 at 06:48:50, Tony Werten wrote:

>On January 07, 2003 at 05:47:37, Ed Schröder wrote:
>
>>On January 07, 2003 at 05:05:31, Tony Werten wrote:
>>
>>>Hi Ed,
>>>
>>>your board tables seem to ignore xray attacks.


>>xray attacks are done, it's only not mentioned as I thought it would be
>>self-understood.

>I don't see how they are combined with the boardtables to find hanging pieces.
>
>Adding them as normal attacks will make you go wrong as often as not counting
>them at all, is my guess.

Let's go through a couple of xray examples:

[d]rn1qkbnr/pbppp1pp/1p3p2/8/2B5/1QP1P3/PP1P1PPP/RNB1K1NR b KQkq -

The knight on G8 is hanging, 2 attackers, one defender, the lowest attacking
piece is a bishop. You can extract this from the bit settings.







[d]r2qkbnr/pbppp1pp/1pn2p2/3Q4/2B5/2P1P3/PP1P1PPP/RNB1K1NR b KQkq -

The knight on G8 is not hanging because the lowest attacking piece is a Queen.




[d]rn2kbnr/pppqpppp/3pb3/8/8/P1N4N/1PPPPPPP/R1BQKB1R w KQkq -

The white knight on H3 is well covered, 2 attackers, 2 defenders, the lowest
attacking piece is a bishop, but its defender is lower, a pawn. The white bishop
on F1 looks through G2 to H3.

Hope this helps,

Ed



>Tony
>
>>
>>
>>>Is that because it doesn't matter too much, or because it's mainly used for move
>>>ordering ( so it's only less effective but not wrong ) ?
>>
>>I use xray also for evaluation, for instance for mobilty, king safety, so xray
>>must be done and in an accurate way, I will write a little about it in the
>>mobility section.
>>
>>Ed
>>
>>>Or do you handle xray attack as a normal attack ?
>>
>>
>>>Cheers,
>>>
>>>Tony



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